n, s = input(), input()
print(s[:s.count("R")].count("W")) n, s = input(), input() n input() input s input() input print(s[:s.count("R")].count("W")) print s[:s.count("R")].count("W") [:s.count("R")].count [:s.count("R")] s :s.count("R") s.count("R") s.count s count "R" count "W" n, s = input(), input() input() n s = input(), input() input() s
n, s = input(), input()
print(s[:s.count("R")].count("W"))